Personal air sampling pumps and controls are generally known. For instance, U.S. Pat. No. 3,814,552 describes a personal air sampling pump including a solenoid driven rubber diaphragm and rubber flapper check valves to control inlet and outlet flow. The diaphragm has a flexible annulus and a rigid central section and is used with independently timed drive pulses for essentially constant flow with varying load.
Similarly, U.S. Pat. No. 4,063,824 describes a constant flow air sampling pump including a variable drive pump that is connected to a filter and that is driven by an electric motor and is controlled by a feedback circuit of an integrator and an amplifier to maintain a constant flow of air through a dosimeter. The dosimeter is worn by an individual and at the termination of a period of time, such as a work day, the filter is removed and the collected contents are analyzed by conventional techniques such as gas chromatography to determine a level of exposure of the individual using the dosimeter.
Still further, U.S. Pat. No. 4,091,674 describes an electronically timed, positive displacement air sampling pump for use with air sample collecting devices in various environmental conditions. The device provides for average flow rate, independently metered total volume, operating time register and an audible “rate fault” alarm.
U.S. Pat. No. 5,107,713, describes a microprocessor controlled air sampling pump that utilizes a PWM controlled DC electric motor for regulating air flow generated by a diaphragm-type air pump. The control system regulates air flow as a function of the RPM of the motor by establishing a table of values which relate motor RPM to air flow rates. The control system maintains RPM at the desired value but includes a control loop which senses deviations in RPM and adjusts the PWM signals to the motor to regulate RPM.
While the identified devices may generally work for their noted purposes, there is an identifiable need for an improved personal air sampler as disclosed herein.